This invention has been created without the sponsorship or funding of any federally sponsored research or development program.
The present invention is directed to an apparatus for forming a fluid conveying pipe known in the trade as a xe2x80x9cdouble ended upset pipexe2x80x9d. Such a pipe has a forward, or xe2x80x9cpinxe2x80x9d end section, an elongated middle section and a rearward, or xe2x80x9cboxxe2x80x9d end section. The inner diameters of all three sections of the pipe are the same. The outer diameters of the forward and rearward end sections of the pipe are substantially greater than the outer diameter of the middle section of pipe. Therefore, the thickness of the middle section of the pipe is substantially thinner than either of the forward and rearward end sections of the pipe. The extra thickness of the forward and rearward end section of the pipe is machined and/or threaded to enable the forward, or xe2x80x9cpinxe2x80x9d end of a first pipe to be coupled to the rearward or xe2x80x9cboxxe2x80x9d end of a second pipe.
In the past, metallic double ended upset pipes have been formed by extruding the middle and end sections of the pipe separately and welding the forward and rearward end sections to opposite ends of the middle section. Since the welded areas represent potentially weak areas of the pipe, each section of the pipe is made thicker than that which would normally be needed. This procedure is time consuming and expensive. The extra thickness which requires extra material also adds a material cost to the pipe. The added weight of the pipe adds still further costs in shipping and handling.
Many metal extrusion devices and methods have been developed for extruding a pipe from a billet with the use of a press, a die, and a mandrel. However, there is no known apparatus or system for extruding an integral pipe having a uniform inside diameter in which the opposite end sections of the pipe have an outside diameter greater than the outside diameter of the middle section of the pipe. These and other difficulties experienced with the prior art pipe extruding devices or methods have been obviated by the present invention.
It is, therefore, a principal object of the invention to provide an apparatus for extruding a pipe from a metal billet for producing an integrally formed pipe having a constant or uniform inside diameter and a middle section which has a smaller outside diameter than the outside diameter of each of the opposite end section of the pipe.
A further object of the invention is the provision of an apparatus for extruding a pipe from a metal billet as described above in a single continuous extrusion operation.
Another object of the present invention is the provision of a method of extruding a pipe from a metal billet in which the pipe has uniform inside diameter and a middle section having a smaller outside diameter than the outside diameter of the opposite end sections of the pipe.
A still further object of the invention is the provision of a method of extruding from a metal billet a pipe as defined above in a single continuous process.
Still another object of the invention is the provision of having an outside non-uniform configuration mandrel for use in a metal extrusion machine for extruding from a metal billet a pipe having a uniform inside diameter and a middle section which has a smaller outside diameter than the outside diameter of the opposite end sections of the pipe.
Another object of the invention is the provision of an apparatus for extruding a pipe from a metal billet wherein the middle section of the pipe has a smaller outside diameter than the outside diameter of each of the opposite end sections of the pipe and one end section of the pipe has a smaller inner diameter that the inner diameter of the middle section and opposite end section of the pipe.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.
Apparatus for and method of extruding a metal pipe having a substantially uniform inner diameter. The forward and rearward end sections of the pipe are thicker than the middle section of the pipe. A heated metal billet having a cylindrical longitudinal bore is inserted into the rear opening of a cylindrical bore of a stationary container. A two-part removable inner die is located within the bore of the container adjacent the forward end of the container and an outer die is located outside of the container adjacent the front end of the container. The inner die has a relatively small diameter cylindrical bore. The outer die has a relatively large diameter cylindrical bore. The billet is moved along a central longitudinal axis within the bore of the container by a press which includes a circular forward pressing surface and a mandrel extending forwardly from the pressing surface toward the billet. The mandrel has a cylindrical relatively large diameter rearward portion, a cylindrical relatively small diameter middle portion and a frusto conical forward portion which tapers outwardly in the forward direction from the diameter of the middle portion to the diameter of the forward portion. Metal from the billet is forced through the bore of the inner die around the small diameter portion of the mandrel by moving the press forwardly for a first distance for extruding a preliminary forward end section of pipe. The press is moved forwardly for a second distance for forcing metal from the billet through the bore of the inner die around the large diameter rearward portion of the mandrel for extruding the middle section of pipe and causing the preliminary forward end section of pipe to pass over the tapered forward portion of the mandrel. This causes the preliminary forward end section of pipe to be expanded transversely of its central longitudinal axis to an inner diameter which is equal to the inner diameter of the middle section and a wall thickness which is greater than the wall thickness of the middle section of pipe. The inner die is removed from the container and the press is moved forwardly for a third distance for forcing metal from the billet through the bore of the outer die around the rearward portion of the mandrel to extrude the rearward end section of pipe having an inner diameter which is equal to the inner diameter of the middle section of pipe and a wall thickness which is greater than the wall thickness of the middle section of pipe.